In recent years, wireless communication systems have been developed rapidly. For example, wireless Local Area Network (WLAN) technologies based on IEEE 802.11 (i.e. WiFi), a Bluetooth system based on IEEE 802.15, and Femto technologies oriented to indoor applications that are derived from a mobile communication system have been widely used.
The WiFi technology based on IEEE 802.11 is the most extensively used wireless network transmission technology at present. A WiFi system is defective for its relatively low system efficiency and significant waste of wireless resources due to the employment of a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism. An essential reason for such a defect lies in that the CSMA/CA mechanism is a random multi-access mechanism based on competition, and there exist competitions for the access right to wireless resources between a Central Access Point (CAP) and a Station (STA) or between different STAs due to the CSMA/CA mechanism. Simultaneous competitions for a wireless channel will result in a collision, thus leading to the wireless resource waste. To avoid such collision, the CSMA/CA mechanism requires the CAPs or STAs to retreat randomly from the competition for the wireless channel. If all of the CAPs and STAs retreat, the wireless channel is not utilized even it is idle, causing significant waste of the wireless channel. Therefore, the system efficiency of IEEE 802.11 is relatively low. For example, although the peak rate at the physical layer in an IEEE 802.11g system may reach 54 Mbps, the reachable peak rate of a large-packet download service at the Transmission Control Protocol (TCP) layer is no more than 30 Mbps. Despite of the above defects, the IEEE 802.11 system is flexible and does not rely on a centralized control mechanism, so that the device costs are relatively low.
A Femto technology based on 3GPP standards, which is derived from a mobile communication system, is a new technology intended for indoor coverage. Since about 70% of data services is conducted in doors according to data statistics of the 3G system, an indoor high-speed data access solution is especially important. A Femto base station, which is named as a Pico Base Transceiver Station, is small in volume (like in WiFi technologies) and flexible in deployment. The Femto base station inherits almost all features of a mobile communication system due to its derivation from the mobile communication system. Considering its limited coverage range and a relatively small number of access users, the Femto device is designed with a decreased processing capability, to reduce the device costs. In terms of a duplexing manner, Femto base stations may operate in two duplexing mechanisms, i.e. a Frequency Division Duplexing (FDD) and a Time Division Duplexing (TDD), just like the mobile communication system. Because FDD uplink and downlink carrier resources are symmetric, certain resource waste is caused for a data service in a FDD system due to a service feature that uplink and downlink data flow of the data service are asymmetric. In a TDD system, however, both uplink and downlink operate at the same carrier, and different wireless resources are allocated for the uplink and downlink through the division of time resources, thus the TDD system can be more suitable for a data service characterized by asymmetric uplink and downlink service demands, in comparison with an FDD system. In the mobile communication system (including a Femto system), however, due to the static allocation of uplink and downlink resources in the TDD duplexing manner, it is difficult to implement dynamic matching between service demands and resource division in the case of various data services with different demands, such as web surfing, mobile videos and mobile games. Due to the employment of a centralized control mechanism based on scheduling, and hence there is no wireless resource waste that is caused by competition collision between the Base Station or CAP and a User Equipment or between User Equipments and random retreat, the Femto technology is advantageous for a higher link efficiency in comparison with the WiFi technology.
For overcoming the consideration of factors such as path loss, demand for uplink transmission open-loop power control exists for wireless communication systems.